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. 2019 May 7;292(1):129–137. doi: 10.1148/radiol.2019182176

Figure 3a:

Figure 3a:

Ferumoxytol-labeled and unlabeled matrix-associated stem cell implants (MASIs) in a Göttingen minipig. (a) Sagittal image from proton density–weighted MRI (repetition time msec/echo time msec, 3700/30) of the distal femur with ferumoxytol-labeled MASIs in cartilage defects (arrows) shows hypointense signal in the MASIs compared with the adjacent healthy cartilage. (b) Corresponding color-encoded T2 map overlaid on a sagittal T2-weighted spin-echo image (3500/60) shows shortened T2 relaxation times of ferumoxytol-labeled MASIs (arrows) compared with the adjacent cartilage. (c) Corresponding photograph of macroscopic specimen of the same knee joint at 12 weeks after surgical implantation shows partial cartilage regeneration of the defects (circles). (d) Sagittal image from proton density–weighted MRI (3700/30) of the distal femur with unlabeled MASIs (arrows) shows iso- to hyperintense signal compared with the adjacent healthy cartilage. (e) Corresponding color-encoded T2 map overlaid on a sagittal T2-weighted spin-echo image (3500/60) shows similar T2 relaxation times of unlabeled MASIs (arrows) compared with the adjacent cartilage. (f) Corresponding photograph of macroscopic specimen at 12 weeks after surgical implantation shows no difference in cartilage regeneration outcomes (circles), indicating no negative effects of the iron label on the MASIs. (g) Scatterplot of results of histopathologic analysis of joint specimen at 12 weeks after implantation of ferumoxytol-labeled and unlabeled MASI, as assessed with the Pineda score (a cartilage histologic scoring system based on four factors of filling defect, reconstruction of the osteochondral junction, matrix staining, and cell morphology) (P = .35, indicating no difference in cartilage defect repair outcomes between labeled and unlabeled MASIs). (h) Scatterplot of results of collagen type 2 staining, measured as positively stained pixels in the histopathologic specimen (P = .79, showing no difference in cartilage defect repair outcomes between labeled and unlabeled MASIs). Data are means and standard errors of the mean for labeled and unlabeled MASIs.